
class Counter1 {
    public static int counter;
    public int getCounter1() {
        return counter;
    }
    public void add() {
        counter++;
    }
}
public class ThreadDemo16 {
    public static void main(String[] args) throws InterruptedException {
        Counter1 counter1 = new Counter1();
        Thread t1 = new Thread(() -> {
            synchronized (counter1) {
                for (int i = 0; i < 10000; i++) {
                    counter1.add();
                }
            }
        });

        Thread t2 = new Thread(() -> {
            synchronized (counter1) {
                for (int i = 0; i < 10000; i++) {
                    counter1.add();
                }
            }
        });

        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println(counter1.getCounter1());
    }
}
